hmm. this same kind of thing happened to mine, but it ended up being that the ROM i was using (not stock) had this functionality built in, and the wifi-tether app interfered. but obviously, this doesn't quite fit your problem. sorry :/
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jlehenbauerSep 12 '11 at 19:44

Open Radiocom. This was the first time I opened the app, and a splash screen asked for me to "select which MA to use." I couldn't find the MA mentioned in the thread in this list, so I just selected 3G All Others (or something like that).

I guess I had the WiFi Tether still running in the background so I had to do this twice. For others who already have WiFi Tether 3.1-beta6 loaded, reboot your phone first then follow josh3736's instructions. Worked great on my Verizon Droid 2 Global after the 2.3.3 OTA update.
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user8097Sep 18 '11 at 15:47

Since the 4.5.605 update to Droid X, this seems to be doing the trick so far (10 minutes in). Thanks for the hack! josh3736 FTW
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user8356Sep 29 '11 at 3:52

Yes, I was rooted. Before the update, I manually unrooted (z4root) to ensure the update went smoothly, and after the update, I re-rooted with the Droid 3 one-click root. I am rooted properly (Titanium Backup works).
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josh3736Sep 8 '11 at 2:36